1. Field of the Invention
The present invention relates to a method for processing waste copper liquid to produce high copper content sludge, and more particularly to the process of classifying the waste liquid from PCB production into an acidic low copper content waste liquid, an acidic high concentration copper content waste liquid and an oxidized acidic high concentration copper waste liquid, and mixing the waste liquid with a strong alkali to raise the content of copper in the sludge, thereby improving the economical values of the recycle.
2. Description of the Prior Art
Following the development and popularization of electronic information products, the PCB output value already exceeded NT$100 billion, and aside from a plurality of organic pollutants in the waste water, waste liquid and other disposables resulting from the use of chemicals and special raw materials for PCB production process, substantial quantities of copper, lead and nickel in copper compounds are also included. If such voluminous heavy metals are not properly treated, serious environmental pollution could be caused and even pose a serious threat to human health.
Presently, the PCB manufacturers would first neutralize the pH value of the discharged low copper content waste liquid and then remove water until it reaches the regulated standard for discharge; afterwards, the copper sludge would be outsourced to specialized companies for extraction and recycling of copper. Since treatment fees charged by the outsourced companies are based on the weight of the copper sludge, such charges could be a heavy burden on the PCB manufacturers if the copper content of the sludge is not raised. Following continuous accumulation of disposables, it is critical to resolve the generation of disposables, raise its value for recycling and minimize the impact to the environment by reducing the disposables or completely recycle and reuse the disposables, thereby minimize the threat by disposables to the quality of our living environment.
PCB manufacturers use huge quantities of copper for the production of PCB; during the production process, etching, surface treatment and other processes generate acidic low concentration copper waste liquid and acidic high concentration copper waste liquid and oxidized acidic high concentration copper waste liquid, therefore, it is necessary to improve the treatment method of conventional waste liquid in order to raise the copper content of the sludge to make it valuable for recycle. Presently, however, no recycling flow is available for both treating the low copper content waste liquid and also effectively converting the copper waste liquid and derivative copper sludge into cupric oxide (CuO) with high recycle value. To raise the value of disposables for recycling and to resolve the problem of output of sludge onsite in the factory can avoid the entailed cost and risk in outsourcing.
Referring to FIG. 1, the conventional method of PCB manufacturers for treating copper waste liquid is mainly by direct mixing of acidic low concentration copper waste liquid (for example, washing waste water with copper content) and acidic high concentration copper waste liquid (such as copper sulfate waste liquid, copper nitrate waste liquid, sodium persulfate light etching waste liquid (SPS waste liquid), sulfuric acid chlorine dioxide light etching waste liquid (G5B waste liquid) and cupric chloride waste liquid, etc), then add sodium hydroxide (NaOH) to adjust the pH value to 8.5˜9.5; afterwards, add coagulating agent (such as ferric chloride (FeCl3) or use backflow of copper sludge as substitute); further, add polymer for cementing and form copper hydroxide (Cu(OH)2) (with copper content 1-2% and water content 98%), and use a dryer to remove water to reduce the water content to 70% (with copper content only 3%˜10%), and again use an oven to further lower the water content to 40% and obtain copper hydroxide (Cu(OH)2) with copper content between 7%-15%.
However, this treatment method is mainly used to discharge the copper ions in the waste liquid so it forms solid copper hydroxide sludge (Cu(OH)2) and the copper content is only 5˜15% with no recycle value and yet has to pay very stiff treatment costs.